1. Field of the Invention
The present invention relates to a resist underlayer film composition to be used in a multilayer resist step which is used for a fine patterning in a manufacturing step of a semiconductor apparatus, etc., or an organic film composition effective for a planarizing composition for manufacturing a semiconductor apparatus, a process for forming a film using the same, a patterning process using the underlayer composition suitable for exposure by far ultraviolet rays, KrF excimer laser (248 nm), ArF excimer laser (193 nm), F2 laser (157 nm), Kr2 laser (146 nm), Ar2 laser (126 nm), soft X-rays (EUV), electron beam (EB), an ion beam, X-rays, or the like, and a compound for forming an organic film useful as a component of the film composition.
2. Description of the Related Art
With a tendency of high integration and high-speed of LSI, a finer pattern size is required. Along with the requirement of finer pattern size, the lithography technologies have accomplished fine patterning by using light sources with shorter wavelength and properly selecting resist compositions corresponding to the light source. As for such compositions, positive photoresist compositions used as a monolayer are mainly selected. Each of these monolayer positive photoresist compositions has a skeleton providing an etching resistance against dry etching with chlorine-based gas plasma or fluorine-based gas plasma in the resist resin, and has resist mechanism that an exposed area turns soluble, thereby forming a pattern by dissolving the exposed area and dry etching a substrate to be processed to which the resist composition is applied by using the remained resist pattern as an etching mask.
However, when a pattern become finer, that is, a pattern width is changed narrower, without changing the thickness of a photoresist film to be used, resolution performance of the photoresist film is lowered. In addition, developing the pattern of the photoresist film with a developer causes a pattern fall because a so-called aspect ratio of the pattern becomes too high. Therefore, the thickness of a photoresist film has been made thinner along with advancing a finer pattern.
On the other hand, for processing a substrate to be processed, a method to process the substrate by dry etching by using a pattern-formed photoresist film as an etching mask is usually used. Actually however, there is no dry etching method capable of providing an absolute etching selectivity between the photoresist film and the substrate to be processed. Therefore, the resist film is also damaged and fallen during processing the substrate, so that the resist pattern cannot be transferred to the substrate to be processed correctly. Accordingly, as a pattern becomes finer, it has been required that a resist composition has a higher dry etching resistance. In addition, the use of shorter wavelength exposure radiations has required resins used for photoresist compositions to have low absorbance at the wavelength to be used for the exposure. Accordingly, as the radiation shifts from i-beam to KrF and to ArF, the resin shifts to novolac resins, polyhydroxystyrene, and resins having an aliphatic polycyclic skeleton. Along with this shift, an etching rate of the resin actually becomes higher under the dry etching conditions mentioned above, and recent photoresist compositions having a high resolution tend to have a low etching resistance.
As a result, a substrate to be processed has to be dry etched with a thinner photoresist film having lower etching resistance. The need to provide a composition for this process and the process itself has become urgent.
A multilayer resist process is one of solutions for these problems. This method is as follows: a middle layer film having a different etching selectivity from a photoresist film, that is, a resist upper layer film, is set between the resist upper layer film and a substrate to be processed, and then, to obtain a pattern on the resist upper layer film; the resist upper layer pattern is transferred to the middle layer film by dry etching by using the upper layer resist pattern as a dry etching mask; and then the middle layer pattern is transferred to the substrate to be processed by dry etching by using the middle layer film as a dry etching mask.
The multi-layer resist process further include a three-layer resist process which can be performed by using a typical resist composition used in a monolayer resist process. For example, this method is configured to form: an organic film based on novolac or the like as a resist underlayer film on a substrate to be processed; a silicon-containing film as a resist middle layer film thereon; and a usual organic photoresist film as a resist upper layer film thereon. Since the organic resist upper layer film exhibits an excellent etching selectivity ratio relative to the silicon-containing resist middle layer film for dry etching by fluorine-based gas plasma, the resist pattern is transferred to the silicon-containing resist middle layer film by means of dry etching based on fluorine-based gas plasma. Further, since the silicon-containing resist middle layer film exhibits an excellent etching selectivity ratio relative to an organic underlayer in the etching using an oxygen gas or a hydrogen gas, film pattern of the silicon-containing middle layer film is transferred to the underlayer by means of etching based on an oxygen gas or a hydrogen gas. According to this process, even when a resist composition which is difficult to form a pattern having a sufficient film thickness for directly processing the substrate to be processed or a resist composition which has insufficient dry etching resistance for processing the substrate is used, a novolac resin film pattern having a sufficient dry etching resistance for the processing can be obtained when the pattern can be transferred to the silicon-containing film.
While numerous process have been known (for example, Patent Document 1) for the organic underlayer film as described above, in recent years, it has now been growing necessity to have excellent filling property and planarizing characteristics in addition to dry etching characteristics. For example, when a basis substrate to be processed has a fine pattern structural composition such as a hole or a trench, it is necessary to have filling property which fills in the pattern with a film without any voids. In addition, when the substrate to be processed as a basis has a step(s), or when a pattern dense portion and no pattern region exist on the same substrate, it is necessary to planarizing the film surface by the underlayer. By planarizing the surface of the underlayer, fluctuation in the film thickness of a middle layer or a photoresist formed thereon is controlled, whereby a focus margin in lithography or a margin in the processing step of the substrate to be processed thereafter can be enlarged.
As a means to improve filling/planarizing characteristics of an underlayer composition, addition of a liquid state additive such as a polyether polyol has been proposed (Patent Document 2). However, the organic film formed by the method contains a large amount of the polyether polyol units, etching resistance of which are inferior, so that the etching resistance of the resulting film is markedly lowered whereby it is not suitable for an underlayer for the three-layer resist. Thus, it has been desired to develop a resist underlayer film composition having both of excellent filling/planarizing characteristics and sufficient etching resistance, and a patterning process using the same.
Also, uses of an organic film composition excellent in filling/planarizing characteristics are not limited only to an underlayer for the three-layer resist, and it can be widely applied as a planarizing composition for manufacturing a semiconductor apparatus, for example, substrate planarizing prior to patterning by nano imprinting, etc. Moreover, for global planarizing during the preparation process of the semiconductor apparatus, a CMP process has now generally been used, but the CMP is a high cost process, so that such a composition can be expected to be a composition which is to bear the global planarizing method to be used in place of the CMP.